This invention relates to a security system for controlling access to a building or secured area. Security systems for buildings are typically available in a variety of types and complexity. Generally, most modern security systems utilize an identification card or badge having encoded data therein. The identification card or badge acts as the xe2x80x9ckeyxe2x80x9d to unlock doors. One seeking to gain access through a locked door presents the identification card or badge to a card reader. If the bearer of the card or badge is granted permission, the door is unlocked.
A security system using electronically detectable identification cards or badges requires a control system that can decode the data encoded in the identification card or badge, and determine the access permission before signalling the actuation of the door lock. A computer-controlled system is typically used. A central computer having a database of access permissions for all active identification cards or badges is employed. These computer-based systems are readily available and are in common use today.
The problem presented to the use of the prior art security systems is the expansion of the system to accommodate growth, and the integration of the security with ancillary systems that would enhance the operation and administration of security within the building or secured area. A security system in a building having public access, for example, may employ a conventional computer-based access control system. To incorporate a fire alarm system to allow for emergency egress, and override the electronic door locks is difficult to perform while still retaining any logic functions in the security system. The typical override in a conventionally integrated system is to shut down the security system, and unlock all doors. This condition, though certainly effective in the event of a fire, may constitute a breach of security in a false alarm situation.
A security system in a hospital may utilize an infant protection system that triggers an alarm when an infant is moved in an unauthorized manner to an exit to the maternity ward. Typically, the infant wears an unobtrusive transmitting unit on its ankle, wrist, or umbilical cord, that is detected by monitors installed at the ward exits. An alarm condition may be used for a signal to lock the door, thereby thwarting any attempted abduction of the infant. While these systems allow for override when an authorized staff member relocates a protected infant, the system and its override control is administered separately from a centralized building control system.
Additionally, integration of a separate infant control system to a door locking security system and a fire alarm system, is logistically difficult to achieve while maintaining any centralized administration. One attempting to abduct an infant need only trigger the fire alarm to create a distraction, and override the door locking functions, to facilitate his misdeeds. Preferably, a system that integrates the fire alarm, infant protection, and door locking system would retain operation in selected areas, allowing for authorized, and controlled, exit at all times.
The invention described herein addresses the need for a flexible and easily adaptable system for controlling the areas of ingress and egress to, from, and within a building or secured area. The use of a programmable logic controller in place of a conventional computer-based central processing unit allows for this needed expandability, modularity, while providing for ease of programming.
Programmable logic controllers are traditionally used in process control applications in manufacturing and industrial environments. They are particularly adapted to controlling steps that occur at specific times and in a specified sequence according to various parameters, or steps that occur in response to specific events.
The programmable logic controller is a computerized relay bank; for a given or expected input, an output signal is generated in response. The logic incorporated into the programmable logic controller may be depicted in the form of a ladder logic diagram. The programmable logic controller steps through the ladder in a scan of its input ports, changing the state of the output ports accordingly.
A programmable logic controller is inherently expandable due to its modular design. Additional ports may be added by merely plugging in a new input-output module into the controller. Additionally, program changes and additions may be readily implemented as a result of the intuitive ladder logic program structure.
The present invention is directed to an apparatus that satisfies the need for a modular and flexible control system for an access and control system for a building or secured area. The use of a programmable logic controller in place of a conventional computer-based central processing unit allows for expandability, modularity, and ease of programming. Ancillary systems may be readily interfaced by coupling to an input port, without having to reconfigure the entire system.
In summary, and in accordance with the above discussion, the foregoing objectives are achieved in the following embodiments.
A programmable logic controller, having a database of personnel information resident in its memory is used to control access through a door to a secured area. The programmable logic controller has a basic module for co-processing functions, and an input-output module. A card reader is placed at the secured door location, and is coupled to the basic module of the programmable logic controller. An electronically actuated door lock that secures the door in a locked state is coupled to an output port of the input-output module. An encoded identification badge is presented to the card reader by one seeking access through the secured door. The encoded identification number from the badge is decoded by the basic module, and compared to the authorization and permissions associated with the identification number in the database. If the permissions associated with the identification number permits access, the door is unlocked by changing the state of the output port coupled to the door lock at the secured door.
In accordance with an aspect of this invention, there is provided the ability to condition the actuation of the door lock through the signalling of an alarm from an ancillary system coupled to an input port of the input-output module. Alarm signals from additional ancillary systems may, in combination, further condition the actuation of the door lock.